KENNEDY SPACE CENTER, FLA. -- Mission STS-117 Mission Specialist Patrick Forrester has donned his launch suit and helmet for a fit check, part of the pre-launch preparations during terminal countdown demonstration test (TCDT) activities. The mission crew is at KSC for the TCDT, which includes a simulated launch countdown. The STS-117 mission is No. 21 to the International Space Station. Mission payloads aboard Atlantis include the S3/S4 integrated truss structure, a third set of solar arrays and batteries. The crew of six astronauts will install the truss to continue assembly of the station. Launch is scheduled for no earlier than March 15. Photo credit: NASA/Kim Shiflett.